CuLator® is designed to reduce, remove, and eliminate stain-causing metals from your spa water. CuLator® will also help prevent spa water turning green or brown and lowers your metal levels down to 0.0! CuLator® SpaPak works in your fresh or salt water spa to eliminate metals and prevent stains for up to 6 months. Either leave the SpaPak in your reservoir continually, or use it when you fill your spa (let it eliminate for a day or two then rinse, dry and reuse). Your choice! Each SpaPak comes with a CuLator® GatorEgg protector. Just make sure you run the pump for an hour the first time you use the product.